This invention relates to a liquid nebulizer, and more particularly to a nebulizer for nebulizing liquid fuel by employing ultrasonic waves.
In the past, nebulizers employing ultrasonic waves have been widely used for spraying liquid fuels such as light oil. A typical structure of such nebulizers is shown in U.S. Pat. No. 3,901,443 issued Aug. 26, 1975. As disclosed in that patent, a liquid container is provided with an outlet duct and an air blower. An ultrasonic transducer is fitted on the bottom of the container and has a predetermined inclination with respect to the surface of the liquid to be nebulized. When ultrasonic waves are radiated into the liquid by operating the transducer, a liquid projection is produced on the liquid surface, and a fog composed of minute liquid particles is formed from the top and circumference of the liquid projection. The fog is exhausted through the outlet duct together with the air flow supplied by the air blower. The transducer is inclined with respect to the liquid surface so that the liquid projection is also inclined; in this way large liquid particles from the top of the liquid projection do not fall back on the top of the liquid projection. As a result, nebulizing efficiency is known to be increased by more than several ten percent compared with nebulizers having transducers fitted horizontally, i.e., with no inclination.
When nebulizers employing ultrasonic waves are used in light oil combustion equipment, a very constant quantity of nebulizing is required in order to maintain proper combustion. In the known structure described above, however, although large liquid fuel particles from the liquid projection do not fall on the top of the liquid projection directly, they fall on the liquid surface directly or from the outlet duct as drops, and cause waves on the liquid surface. As a result, a stable liquid projection cannot be formed, and the quantity of nebulizing spray is varied. Furthermore, since liquid fuel such as light oil is heated more by ultrasonic energy than is water and has poor heat conductivity, the temperature difference is increased between the base of the liquid projection where ultrasonic energy is concentrated and the part where ultrasonic energy is weak. Thus a non-uniform temperature distribution between the transducer and the liquid surface occurs when drops of heated liquid fuel fall from the liquid projection and ultrasonic waves radiated from the transducer are reflected and refracted, lose directivity, and do not focus on the liquid surface, resulting in variation of nebulizing quantities and action.
An object of the present invention is to provide a liquid nebulizer producing a stable quantity of nebulizing fog by preventing the rise of waves on the liquid surface where the liquid projection is formed and by supplying thermally uniform liquid to the part of the liquid where ultrasonic waves are transmitted. This object is achieved by utilizing a partition that surrounds the liquid projection, confining particles from the liquid projection and drops from the outlet duct outside the region of the liquid projection.
The embodiments of the present invention are described as follows: